2001 V70 T5, has a check engine light on, the scanner reads ECM 4308 MAJOR LEAK. The guy said it was a J Hose on the Canister. Is it located under the car near the back right wheel? And is that the problem or maybe gas cap gone bad?

 

There is about 10 different things that can lead to that code.
The J-hose is one of them and the cap can be another.